CanvasPattern.setTransform() - Web APIs 编辑

The CanvasPattern.setTransform() method uses an SVGMatrix or DOMMatrix object as the pattern's transformation matrix and invokes it on the pattern.

Syntax

void pattern.setTransform(matrix);

Parameters

matrix

An SVGMatrix or DOMMatrix to use as the pattern's transformation matrix.

Examples

Using the setTransform method

This is just a simple code snippet which uses the setTransform method to create a CanvasPattern with the specified pattern transformation from an SVGMatrix. The pattern gets applied if you set it as the current fillStyle and gets drawn onto the canvas when using the fillRect() method, for example.

HTML

<canvas id="canvas"></canvas>
<svg id="svg1"></svg>

JavaScript

var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');

var svg1 = document.getElementById('svg1');
var matrix = svg1.createSVGMatrix();

var img = new Image();
img.src = 'https://www.wenjiangs.com/wp-content/uploads/2020/mozilla/Canvas_createpattern.png';

img.onload = function() {
  var pattern = ctx.createPattern(img, 'repeat');
  pattern.setTransform(matrix.rotate(-45).scale(1.5));
  ctx.fillStyle = pattern;
  ctx.fillRect(0, 0, 400, 400);
};

Note that newer browser versions started to support DOMMatrix as an input to setTransform(), so for example you could replace the SVGMatrix in the above example with the following:

const matrix = new DOMMatrix([1, .2, .8, 1, 0, 0]);

Edit the code below and see your changes update live in the canvas:

Playable code

<canvas id="canvas" width="400" height="200" class="playable-canvas"></canvas>
<svg id="svg1" style="display:none"></svg>
<div class="playable-buttons">
  <input id="edit" type="button" value="Edit" />
  <input id="reset" type="button" value="Reset" />
</div>
<textarea id="code" class="playable-code" style="height:120px">
var img = new Image();
img.src = 'https://www.wenjiangs.com/wp-content/uploads/2020/mozilla/Canvas_createpattern.png';
img.onload = function() {
  var pattern = ctx.createPattern(img, 'repeat');
  pattern.setTransform(matrix.rotate(-45).scale(1.5));
  ctx.fillStyle = pattern;
  ctx.fillRect(0, 0, 400, 400);
};</textarea>

var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
var textarea = document.getElementById('code');
var reset = document.getElementById('reset');
var edit = document.getElementById('edit');
var code = textarea.value;

var svg1 = document.getElementById('svg1');
var matrix = svg1.createSVGMatrix();

function drawCanvas() {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  eval(textarea.value);
}

reset.addEventListener('click', function() {
  textarea.value = code;
  drawCanvas();
});

edit.addEventListener('click', function() {
  textarea.focus();
})

textarea.addEventListener('input', drawCanvas);
window.addEventListener('load', drawCanvas);

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• The interface defining this method: CanvasPattern
• SVGMatrix
• DOMMatrix